Drive system

ABSTRACT

A drive system for driving accessories associated with the engine of a vehicle and controlled by the speed of the engine crankshaft, constructed such that the rpm of each accessory is substantially constant over at least the major portion of the normal vehicle operating range regardless of increase in the rpm of the engine and its crankshaft. The drive is so constructed that the input rpm to each accessory increases at substantially the same rate as the rpm of the crankshaft to a first, predetermined speed; then the input to each accessory is substantially constant thereafter regardless of increasing engine speed to a second predetermined crankshaft speed. This second predetermined speed preferably corresponds essentially to the established national speed limit.

BACKGROUND OF THE INVENTION

Modern vehicle engines have been called upon to drive an increasingnumber of accessories as the sophistication of modern vehiclesincreases, which accessories include many convenience items demanded bythe customer.

Generally the accessory drive provides at least a linear ratio betweenthe speed (rpm) of the engine and the speed (rpm) of the accessorydriven shaft. At low engine speeds, no serious problems exist; but athigh engine speeds serious problems exist. Because of this relationship,it is imperative to construct the accessory with proper bearings, sothat it can operate at elevated speeds without an undue limitation onits life. The strength and size of rotating parts must be such thatextremely high speeds do not rupture them. In addition, the widevariation in operating speed of an accessory at times creates a demandfor sophisticated control systems. Such construction makes the accessorymore expensive than necessary or desirable both as original equipment(OEM) parts and as replacement parts. Driving the accessories at veryhigh speeds results in a substantial decrease in the efficiency of thevehicle because a substantial percentage of the output is required forthe accessory drive, which can amount to up to about 30% of the enginehorsepower at moderate speeds. This is extremely wasteful because thepresent fixed ratio drives results in accessory speeds which are notrequired for proper operation of the accessories.

This problem becomes even more severe in some modern engines which areof relatively low horsepower and which operate at relatively highspeeds. Further, the lack of efficiency of the system requires the useof more gasoline--a needless and serious waste of energy. In addition,each accessory normally has a most efficient or optimum RPM range andwith normal systems the accessory is not within this range due to widevariation in the input speed.

Various energy saving types of accessory drives have been proposed. Forexample, the drive between the engine and the fan for cooling theradiator has been thermostatically controlled. This type of drive istemperature dependent and has no relation to engine shaft speed. Suchdrive is not suitable for alternator or generator drive because theseaccessories must be driven continuously when the engine is operating.Other types of drives employ slipping friction clutches; while they maybe successful, they have not found acceptance because of the cost of thedrive and energy losses during operation.

For an accessory drive system to meet requirements for use in modernvehicles, it should be small enough to fit in present-day enginecompartments without any substantial modifications, it should berelatively inexpensive, it should be susceptible of mass production andadjustable to modern assembly techniques, it should have long life, andit should produce a drive from the engine to the accessories whichincreases their speeds in approximately a linear relation withincreasing engine speed at low RPM but which produces relativelyconstant accessory speeds as the engine speed increases above apredetermined point throughout the normal vehicle driving range. Thepresent invention meets all these criteria.

The drive of this invention is to be distinguished from the conventionalvariable pulley transmission as is presently used in, for example,off-the-road vehicles or has been proposed for the transmission fortransmitting power from an engine to the driving mechanism of a vehicle,whether they are wheels, lugs or other devices. In such priortransmissions, the engine rpm is increased and, at the same time, therpm of the driving mechanism is increased at an even faster rate.Further, until a certain driveR pulley rpm is acheived, no power istransmitted to the driveN pulley.

THE INVENTION

This invention relates to a drive system for transmitting torque from aprime mover, such as an automobile engine, to accessories associatedtherewith. It comprises, a relatively inexpensive assembly of variablediameter pulleys connected by a drive belt. The assembly is preferablyconstructed mainly of stamped metal parts; the belt is generally theonly part which will require replacement even after a considerablelength of operating time.

More specifically, the drive system of the present invention comprises apair of variable pitch diameter pulleys, one, a driveR, associated withthe drive shaft and another, a driveN, associated with a driven shaft(which drives the "accessory package"). Each of the variable pulleys hasa fixed flange and a movable flange. The movable flange of each pulleyis mounted on its associated shift by a bushing, preferably constructedof a non-metallic material such as nylon or the like. A suitablypreloaded disc spring urges the movable flange of the driveN pulleyaxially toward the fixed flange thereof. The movable flange of thedriveR pulley is associated with a disc spring having a plurality ofattached weights. The spring, in its rest position, urges the movableflange of the driveR pulley toward the fixed flange thereof. At apredetermined speed, the weights move outwardly because of centrifugalforce, and the movable flange is urged axially away from the fixedflange. The movement of the weights is limited by stop means, and thusaxial movement of the movable flange from its associated fixed flange isalso limited.

Movement of the movable flanges of the pulleys permits the drive beltconnecting the pulleys to shift positions relative to the respectiveshafts and thus provide a different drive ratio between the shafts.

The weights which control the accessory drive mechanism are on thedriveR pulley only, so that the control of speed ratios between thepulleys is from the driver only, i.e., from the drive shaft. As such,the device is drive shaft speed sensitive.

The spring rate of the driveR disc spring is substantially continuouslypositive in slope and the spring has a h/t ratio of about one (1), whereh is the initial formed height and t is the thickness of the spring.

In the specific embodiment described here, and as graphicallyillustrated in FIG. 6, the driveR and driveN pulleys rotate at a fixedratio at relatively low motor speeds, as for example, up to about 1000rpm. At about 1000 rpm, the weights attached to the disc spring of thedriveR pulley begin to move outwardly. As they so move, the driveRpulley continues to rotate at the same speed as the drive shaft whilethe driveN pulley rotates at a substantially uniform speed of about 1000rpm. This condition prevails until the drive shaft speed becomes veryhigh, normally associated with vehicle speeds in excess of the nationalspeed limit. At an elevated speed, such for example, at about a driveshaft speed of 3000 rpm, the weights have reached their most outwardpositions, and thereafter the speed of the driveN pulley then increaseswith further increases in the drive shaft speed but at a reduced lowerratio as compared to the drive shaft speed. In automobiles built in theUnited States of America the crankshaft speed, at a vehicle speed ofabout 55 miles per hour, is generally below 3000 rpm. Thus, in thisspecific example, over the usual crankshaft speed range of about 1000 to3000 rpm, the accessories which are each driven at different rpms(determined by the diameter of the specific pulley associatedrespectively therewith) depending on their function are generallyrotated at substantially constant rpms. Thus according to thisinvention, each accessory can be driven at its optimum or maximumefficiency rpm range over the usual crankshaft speed range of thevehicle.

A device constructed according to this invention and according to thespecific embodiment installed in a 1974 Nova has been road tested for atleast 15,000 miles. During the road testing, all accessories includingair condition have been operated. An energy savings of about 10% hasbeen realized as compared with the same vehicle with the standardaccessory drive driving the same accessories.

THE DRAWINGS

FIG. 1 is a sectional view (parts of which are omitted for clarity)through a drive system according to this invention at idle position;

FIG. 2 is a sectional view (parts of which are omitted for clarity)through a drive system according to this invention at one operatingposition;

FIG. 3 is a plan view of a disc spring useable in the system of FIG. 1;

FIG. 4 is a sectional view of the spring of FIG. 3 taken on line 4--4 ofFIG. 3 illustrating the spring before being loaded in the driveassembly;

FIG. 5 is a view of a pilot hub of the invention;

FIG. 5a is a perspective view of the outlined portion of FIG. 5;

FIG. 6 is a set of curves of a specific drive system, drive rpm plottedagainst equivalent accessory driven rpm or, alternatively, accessorydrive shaft rpm, one curve of which is the usual linear relationship andthe other of which is a curve obtained using the system of thisinvention;

FIG. 7 is a curve in which load is plotted against deflection of adriveR spring for a specific drive system for a drive constructedaccording to this invention;

FIG. 8 is a curve in which load is plotted against deflection of adriveN spring for a specific drive system for a drive constructedaccording to this invention;

FIG. 9 shows spring rate curves of a coil spring, a positive rate discspring as used in this invention, a zero rate disc spring, and a typicalBelleville spring; and

FIG. 10 is a curve showing the speed relationship between the driveR andthe driveN pulleys in a conventional variable pulley transmission.

DETAILED DESCRIPTION

In FIG. 1 there is illustrated a preferred embodiment of the invention.Illustrated there is a drive shaft 10 adapted to be connected to thecrankshaft 11 through the usual vibration damper 12 of, for example, anautomobile engine (not shown). Associated with the crankshaft is avariable driveR pulley, generally identified as 13, which comprises afixed flange 14 and a movable flange 16. The flange 14 is received on areduced shaft portion 18 on drive shaft 10 to abut a shoulder 20 formedin the drive shaft. Flange 14 is held in position on shaft 10 by a bolt22 in threaded engagement with a threaded bore 24 and a washer 26. Themovable flange 16 is press fitted onto a cylindrical sleeve 30 mountedon a bushing means 32 surrounding the shaft 10. The bushing means 32 ispreferably constructed of a suitable material, such as nylon or the likeand may comprise a single part. The flange 16, together with the sleeve30, is axially movable relative to the fixed flange 14 and the shaft 10.A pivot or drive hub 34 is fixed to a cylindrical portion 36 of theflange 16, as for example by welding.

The hub 34 comprises essentially a thrust ring or washer 38 with fingersor drive tangs 40 extending therefrom.

An actuator mechanism for the movable flange 16 is provided and includesa cup-shaped, spring retainer or drive member 42 preferably of stampedsteel is fixed to shaft 10 as for example by welding, and bolted to thevibration damper 12; the periphery of the retainer 42 terminates in anenlarged rim 44. The rim 44 receives and is frictionally engaged by theouter peripheral rim of a disc spring 46. Thus a frictional drivingconnection is established between the disc spring and the rim of theretainer. As illustrated in FIGS. 3 and 4 spring 46 has a plurality ofinwardly extending fingers 54 which terminate in a central opening 48 ofa dimension to surround the sleeve 30. A plurality of radial slots 50,each of which terminate in an enlarged opening 52 at the outer enddefine the plurality of radial fingers 54. A plurality of weights 56having portions extending through the openings 52 are attached, as byswaging, coining, riveting, or the like to the spring 46, and the spring46 is coupled to the movable flange 16 by means of the pivot hub 34,i.e., a tang 40 extends through a slot 50 and a finger engages the outersurface 58 of the washer 38, the surface 58 acting as a fulcrum, as willbe explained. One weight 56 per opening 52 may be provided; a lessernumber of weights can be used, as necessary to perform the function tobe described.

The actuator mechanism for the movable flange 16 thus includes the sheetmetal drum 42 described above as a spring retainer or drive memberhaving disposed therein disc spring 46 and weights 56.

The length of the cylindrical portion 36 is chosen to properly pre-loadthe spring 46. In its pre-loaded condition, the spring is compressedfrom its initial formed condition, thus lessening the height of thecone, as such, it maintains pressure on the movable flange 16 to preventslippage between the drive belt 88 and the pulley flanges 14 and 16.

It is to be understood that other structure can be provided to pre-loadthe spring 46, as for example, various machined threaded sleeves andnuts; however, such structure adds to the cost of the apparatus anddefeats a main objective, i.e., to provide an apparatus which is bothinexpensive and effective for its intended purpose.

Torque transmission between the fixed pulley flange 14 and the movablepulley flange 16 occurs due to friction between the outer rim of thedisc spring 46 and the corresponding rim 44 of the retainer 42. Thereare no torque pins, torque transmitting bushings or keys, thuseliminating any wear, fretting or failure that may occur because ofbending, twisting and binding when such elements are used. The describedstructure eliminates splines and drive lugs which have to slide underload and which require lubrication. Thus the structure eliminates theneed for such lubrication.

FIG. 1 also illustrates a driven shaft 70, suitably supported byappropriate journals (not shown), having affixed thereto, forillustrative and exemplitive purposes only, a multi-bladed fan 72. Thefan 72 has a circular hub 74 and is affixed to the shaft 70 by a nut 76engaging a threaded portion 78 of the shaft 70. The fan 72 may be keyedor otherwise positively connected to the shaft 70 if necessary ordesirable. A pulley 80 is affixed to the shaft 70 by a hub 81 andreceives one or more V-belts (not shown) for driving one or moreaccessories, for example, a water pump, air conditioner compressor,generator, power steering pump or the like (not shown). The pulley 80 isillustrated as being constructed of stamped sheet steel, it may beconstructed of cast iron, or other suitable material without departingfrom the spirit of the invention.

Thus by sizing the driven pulley at each accessory each accessory may bedriven at a different speed which would of course be the optimum ormaximum efficiency speed for that accessory; for purposes ofdescription, this is related to "equivalent accessory speed" or thespeed of the shaft 70.

Associated with the driven shaft 70 is a variable driveN pulley,generally identified as 82, which comprises a fixed flange 84 and amovable flange 86. Torque is transmitted from the pulley 13 to pulley 82by a drive belt 88 of usual construction. The frictional engagementbetween the sides of the belt and the flanges provides the torquetransmission. The fixed flange 84 is illustrated as being spot welded tothe pulley 80; optionally, it may be an integral part if desired.

The movable flange 86 has a cylindrical hub portion 90 which surrounds acylindrical portion 92 of the pulley 80. A bushing 94, constructed ofnylon or the like, is interposed between the portion 92 and the hub 90.The movable flange 86 has a forwardly extending rim 96 which is receivedin a cup-like shroud 98 having a cylindrical hub or bearing support 100surrounding the shaft 70. A bearing 102 is positioned between the hub100 and a sleeve 101 surrounding the shaft 70. Abutting the forwardlyextending rim 96 of the flange 86 of the pulley 82 and within the shroud98 is a disc spring 104 of a construction similar to the disc spring 46,earlier described. Because of the similarity, the spring 104 is notseparately illustrated as is the spring 46. The spring 104 has aplurality of radially inwardly extending fingers 112 which terminate ina central opening 106 of a size to be positioned over the shaft 70. Thespring 104 has a plurality of open-ended slots 108 each terminating inenlarged openings 110 and defining the radial fingers 112. A pivot ordrive hub 114 similar to that illustrated in FIG. 5 surrounds the shaft70, and is clamped to the shaft 70 by the sleeve 101 and hubs 74 and 81.The hub may be keyed or otherwise positively connected to the shaft 70,if necessary or desirable. The hub 114 has fingers or tangs 116 each ofwhich engages a slot 108 and arcuate surfaced pivot portions 118, eachhaving a surface 120 engage the face 112 of a spring finger 112. Thepivot surfaces 118 act as fulcrums for the spring 104. It is to be notedthat like the drive pulley arrangement no disc pins, torque pins or keysare used to connect the spring 104 to the flange 86; only frictioncouples the spring 104 to the flange 86 and the shroud 98. The reasonsfor eliminating such connections are the same as described with respectto the drive pulley arrangement.

The spring 104 is pre-loaded by the selecting the length of the sleeve101 and shoulder 81 and by tightening the nut 76 to properly positionthe parts as is illustrated in FIG. 1, (the idle condition). The springis pre-loaded to a degree that it passes through center and such that italways exerts a force against the flange 86.

As with the spring 46, other structures can be provided to preload thespring 104 if desired.

The drive belt 88 provides the drive between the driveR pulley 12 andthe driveN pulley 82, the drive ratio between the pulleys 13 and 82being dependent on the position of the drive belt 88 relative thereto,which is dependent on the spacing of the flanges of the pulleys 12 and82.

The driveN pulley 82 always maintains tension against the belt 88. Theshifting of the flange spacing of both pulleys 13 and 82 is controlledby the speed of the driver shaft 10.

The ratio of the driveR pulley 13 and driveN pulley 82 speeds issubstantially the same (see FIG. 6) from zero engine speed to apredetermined, first, engine speed. As engine speed increases beyondthat first predetermined speed, centrifugal force causes the weights 56to deflect outwardly gradually with increasing force as the speedincreases. The spring 46 gradually from its FIG. 1 position is deflectedtoward the FIG. 2 position.

DriveR rotation causes centrifugal forces to act at the nominal centerof gravity of the weights 56 which are attached to the driveR pulley.The centrifugal force acts through an increasing (changing) effectiveradius due to the geometry of the weights and is balanced against the(positive) spring rates of the driveR and driveN disc springs 46 and104, respectively. The forces acting on the driveR spring cause a changein movable flange axial position and a change in the driveR pulley pitchdiameter. The fixed length belt shifts on the driveN pulley changing thedriveR-driveN speed ratios. The weights, center of gravity geometry,spring rates and flange pressures are selected so as to produce a"controlled" driveN speed responsive to the driveR speeds.

The weights 56 move outwardly, assuming that the engine speed isincreasing, until they contact the spring retainer 42--see FIG. 2--atwhich time the spring 46 has deflected through center to its secondmaximum positon (the first maximum or idle position being as illustratedin FIG. 1).

Thus, after reaching the maximum weight-deflection position, the driveratio again becomes fixed because the belt has reached its FIG. 2position, and a linear ratio, less than the initial 1 to 1 is againestablished between the pulleys. At this maximum weight-deflectionposition, the speed of the driven pulley varies in accordance with thefixed reduced ratio with further increases in the speed of the driveRpulley 13.

To illustrate a typical drive assembly according to this invention andto compare this with the usual drive conditions, input speed in RPM(corresponding to engine crankshaft speed) is plotted against equivalentaccessory speed in RPM in the curve of FIG. 6. The operation of theunique mechanism described herein produces a three segment curve asillustrated by the solid line in FIG. 6. The curve is composed ofsegments a, b, and c each of a different slope.

In looking at this Figure, segment a of the curve shows the drive ratioaccording to this invention to be substantially 1:1.25 at crankshaftspeeds up to about 1000 rpm. At about 1000 rpm the drive ratio begins tochange to maintain a substantially uniform driveN pulley speed, up toabout 3000 rpm represented by segment b. At speeds above 3000 rpm thedrive ratio becomes fixed at a reduced ratio of less than 1 to 1:25 asrepresented by segment c of the curve. The ultimate rpm of the driveNpulley never reaches the rpm of the driveR. The particular curve ofspeed ratios between input speed of about 1000 rpm and 3000 rpm reflectsthe interaction of the several forces of the drive system, i.e., thebelt forces, the spring forces and the centrifugal forces. It can be astraight, horizontal curve under some conditions.

To further explain the operation of the present drive mechanism andassuming that the idle pitch diameters of the driveR and driveN pulleysare of such diameters to provide a 1 to 1:25 drive speed ratio betweenthe driveR and driveN shafts as is the case in the preferred embodiment,the curve is a straight line, as shown by segment a of FIG. 6. At acertain predetermined speed, centrifugal force acts to move the weights56 outwardly toward their maximum outward positions. The effective pitchdiameter of the driveR pulley becomes increasingly smaller since thebelt tension and reduction in spring force will cause the belt to movecloser to the driveR shaft. At the same time, because of reduction inbelt tension and the spring force on the driveN pulley, the effectivepitch diameter of the driveN pulley increases. Thus the interaction ofthe changing pitch diameters establishes a drive between the pulleys inthe rpm range of segment b of the curve of FIG. 6, wherein driveR shaftspeed (rpm) increases have little or no effect on driveN shaft speed(rpm). Thus the driveN shaft continues to be driven at a relativelyconstant speed during the period in which the weights move outwardly (orinwardly when driveR shaft speed decreases to the first predeterminedspeed). When the weights have reached their maximum position, there isno further change in effective pitch diameters of the pulleys and thepulleys are locked together for rotation at that same drive ratio withfurther increases in driveR shaft speed. This fixed ratio is always lessthan the initial ratio, assumed for discussion to be 1 to 1:25. Thesecond fixed ratio can be determined from the lock up speed, of thedriveR shaft which in the illustration is 3000 rpm and the lock up speedof the driveN shaft, i.e., about 1000 rpm (ideally) to be determined bythe particular accessory manufacturer or the manufacturer of thevehicle. Thus in the example described, the lock up ratio or ratioreached at 3000 RPM of driveR pulley to driveN pulley is about 3 to 1.In a specific American made vehicle, for example, a 1974 or 1975 Nova,with standard drive axle ratio, the vehicle speed at a crankshaft speedof about 1300 rpm is approximately 30 miles per hour and at a crankshaftspeed of about 3000 rpm is approximately 75 miles per hour.

When the speed of the driveR shaft decreases to a value of less than3000 rpm the weights begin to move inwardly toward their idle positionand the movable pulley is urged toward the fixed pulley by the springforce. This urges the belt to ride higher in the driveR pulley and atthe same time, the belt tension forces the movable pulley of the driveNpulley to move away from the fixed pulley thereof. There is againestablished the drive ratio in the b portion of the curve of FIG. 6 andthen to the portion of the curve of FIG. 6.

The broken line curve illustrates a conventional drive ratio between thecrankshaft and the driven shaft from which the accessories are driven,i.e., a continual 1 to 1:25 ratio in which the effective speed of theaccessories increases with the crankshaft speed at this fixed ratio.

The disc springs used in the preferred embodiment of this invention havean h/t (formed height of the unloaded spring to thickness) ratio ofabout one, expressed in the same units of measure, as indicated in FIG.4. The spring rate of such disc springs in the preferred embodiment ispositive i.e., is continuously positive in slope as is illustrated inFIGS. 7 and 8; and can be compared to the curves of spring rates ofother types of springs, as for example, typical Belleville springs,corrugated Belleville springs, and typical coil springs, the spring ratecurves of which are illustrated in FIG. 9.

FIGS. 7 and 8 are load v. deflection curves for the preferred embodimentdriveR disc spring 46 and the driveN disc spring 104, respectively.These are the spring curves to produce the results in FIG. 6. While thesprings 46 and 104 are physically similar in construction, except forthickness, they are preloaded to different amounts, as indicated in thecurves when the drive system of this invention is assembled forinstallation in a vehicle.

The spring 46 is preloaded as explained to a particular deflection D; itmust maintain a force on the movable pulley 16 at idle speeds, so thatslippage of the belt is minimized. At a certain crankshaft rpm, thespring 46 is deflected by centrifugal force acting on the weights 56 toa second deflection D-1. The curve between the idle and fully shiftedpositions is positive and generally linear. There is no deflection surgeor snap action; the deflection is gradual.

The spring 104 is loaded through center to a particular deflection d, soas to continually exert a force against the movable pulley flange 86. Asthe tension on the belt 88 decreases due to the change occurring in thedriveR pulley, the flange 86 is urged toward the flange 84, such thatthe deflection of the spring 104 decreases generally uniformily withlittle decrease in load between the preload or idle position (FIG. 1)and the high speed position (FIG. 2). The high speed deflection isindicated as d-1.

The curves of FIGS. 6, 7 and 8 relate to a specific example of the driveof this invention. In this specific example, the specifics of which aregiven by way of illustration and not by way of limitation, the diameterof the driveR pulley 13 is 7.125 inches, the diameter of the driveNpulley 82 is 7.440 inches. The driveR spring 46 has an outer diameter of7.810 inches while the driveN spring 104 has an outer diameter of 7.810inches. Each weight 56 is 90 grams; there are 18 weights, located 0.195inch from the end of each slot in the driveR spring 46. The h/t ratio ofthe driveR spring is 1.024; h being nominally 0.128 inch and t beingnominally 0.125 inch. The h/t ratio of the driveN spring is 1.223; hbeing nominally 0.115 inch and t being nominally 0.094 inch.

The belt used in this example is a 16 26 V 341. This belt is 1 inchwide, has a 26° included angle, is a V-belt with a pitch length of 34.1inches.

Tests to determine the advantages from using this invention have beenconducted by installing drive systems as per the example given in a 1974Chevrolet Nova, 350 C.I.D. engine with an air pump and an automatictransmission and of course, the normal accessories, such as airconditioning, a water pump, power steering, alternator and fan. Testshave been conducted with the air conditioning operating andnon-operating (from the dash controls) and also in a 1975 Chevrolet Novawith the same accessories but having a catalytic converter and no airpump. In both vehicles, the rear axle ratio was 2.73.

A tabulation of results for 1/3 town and rural two lane driving; 2/3freeway driving; average speed 44 mph, is as follows:

1975 NOVA STOCK ACCESSORY DRIVE

1. a/c on: 1833.0 miles; 108.60 gallons gasoline (pump measured); avg.16.87 mpg.

2. A/C off: 1525 miles; 83.40 gallons gasoline (pump measured) avg.18.29 mpg.

ACCESSORY DRIVE ACCORDING TO INVENTION

1. a/c on: 1372.2 miles; 75.80 gallons gasoline (pump measured) 18.12mpg.

2. A/C off: 764.90 miles; 41.05 gallons gasoline (pump measured) 18.63mpg.

Comparison--using this invention

A/c on 8.31% advantage--fuel savings

A/c off 2.31% advantage--fuel savings

1974 NOVA STOCK ASSCESSORY DRIVE

1. a/c on: 773.9 miles; 50.55 gallons gasoline (pump measured); avg.15.31 mpg.

2. A/C off: 759.20 miles; 44.85 gallons gasoline (pump measured) avg.16.93 mpg.

ACCESSORY DRIVE ACCORDING TO INVENTION

1. a/c on: 2264.90 miles; 135.05 gallons gasoline (pump measured) 16.77mpg.

2. A/C off: 3482.6 miles; 201.90 gallons gasoline (pump measured) 17.25mpg.

Comparison--using this invention

A/c on 9.54% advantage--fuel savings

A/c off 1.90% advantage--fuel savings

FIG. 9 illustrates load v. deflection curves for various springs. CurveA is for a typical Belleville spring; note that a portion of the curveis negative. Curve B is a positive rate disc spring; similar to thatused herein. Curve C is a curve for another disc spring having a portionof zero rate. Curve D is an ideal curve for a coil spring a linearrelationship exists between load and deflection; it does not indicateinstabilities which may occur during use which are indicated in thebroken line curve designated D¹.

FIG. 10 illustrates the speed relationship between the driveR and driveNpulleys in a conventional variable pulley transmission. As the driveRrpm increases, the driveN rpm increases at an even faster rate; untilthe driveR pulley rpm reaches a certain value, no power is transmittedto the driveN pulley.

While one specific example of the preferred embodiment of the inventionhas been fully described, other embodiments of the invention and withinits scope will be readily apparent to those skilled in the art.

We claim:
 1. Apparatus for driving accessories disposed between a driveshaft connected to an engine in a vehicle and a driven shaft connectedto one or more accessories; the combination comprising:a first variablepulley rotationally associated with the drive shaft and having a fixedflange connected to the drive shaft and a movable flange movable axiallyof said fixed flange and the drive shaft; means for moving said movableflange axially away from said fixed flange above a predetermined speed,above zero speed, of the drive shaft; said moving means comprising adisc spring biasing said movable flange and centrifugally responsivemeans associated with said disc spring actuated by centrifugal forceabove said predetermined speed of the drive shaft to change the bias ofsaid spring and effect movement of said movable flange; a secondvariable pulley rotationally associated with the driven shaft and theaccessories and having a fixed flange connected to the driven shaft anda movable flange movable axially of said fixed flange and said drivenshaft; a disc spring means urging said movable flange of said secondpulley axially toward said fixed flange thereof; drive means betweensaid variable pulleys effective to provide the drive therebetween withthe drive ratio between the pulleys determined by the position of themovable flanges with respect to their respective fixed flanges; saidapparatus being constructed and arranged to provide substantially afixed ratio drive between the drive and driven shafts at relatively lowdrive shaft speeds and also to provide substantially a constant speed ofthe driven shaft for speeds for the drive shaft above said predeterminedspeed thereof throughout the major portion of the normal vehicleoperating range; said disc spring being coupled by friction at is outerperiphery only to said drive shaft and said disc spring means beingcoupled by friction at its outer periphery only to said driven shaft. 2.A drive mechanism adapted to transmit drive between a drive shaft and adriven shaft comprising:a first variable pulley rotationally associatedwith the drive shaft and having a fixed flange connected to the driveshaft and a movable flange movable axially of said fixed flange and thedrive shaft; means for moving said movable flange axially away from saidfixed flange above a predetermined speed, above zero speed, of the driveshaft; said moving means comprising a disc spring and centrifugallyresponsive means associated with said disc spring actuated bycentrifugal force above the predetermined speed of the drive shaft tochange the loading of said spring and effect movement of said movableflange; a second variable pulley rotationally associated with the drivenshaft and having a fixed flange connected to the driven shaft and amovable flange movable axially of said fixed flange and said drivenshaft; disc spring means urging said movable flange of said secondpulley axially toward said fixed flange thereof; said variable pulleysbeing drivingly connected, the drive ratio between the pulleys beingdetermined by the position of the movable flanges with respect to theirrespective fixed flanges; said disc spring being coupled by friction atits outer periphery only to said drive shaft and said disc spring meansbeing coupled by friction at its outer periphery only to said drivenshaft; whereby said apparatus provides a substantially constant speed ofthe driven shaft for speeds of the driving shaft above saidpredetermined speed thereof throughout the major portion of the normaloperating range of speed of said drive shaft.
 3. In an accessory drive,the combination comprising drive input means associated with theresponsive to the speed of a prime mover, drive output means associatedwith and effective to drive accessories, and speed control meansvariable in response to the speed of said drive input means disposedbetween said drive input means and said drive output means for providinga linear speed drive relationship therebetween below a relatively lowand above zero speed of said drive input means and also for providing acontrolled variable speed drive relationship therebetween oversubstantially the normal range of speed of said drive input means inexcess of said relatively low speed, the variable speed driverelationship being characterized in that the speed of said drive outputmeans remains substantially constant during the speeds of said driveinput means above said relatively low speed over substantially thenormal range of speed of said drive input means in excess of saidrelatively low speed;said speed control means comprising: a firstvariable pulley rotationally associated with said drive input means andhaving a fixed flange connected to said drive input means and a movableflange movable axially of said fixed flange and said drive input means;means for moving said movable flange axially away from said fixed flangeabove said low speed of said drive input means; said moving meanscomprising a disc spring and centrifugally responsive means associatedwith said disc spring actuated by centrifugal force above said low speedof said drive input means to change the loading of said spring andeffect movement of said movable flange; said centrifugally responsivemeans moving outwardly under increasing centrifugal force resulting fromincreasing speed of said drive input means; a second variable pulleyrotationally associated with said drive output means and saidaccessories and having a fixed flange connected to the drive outputmeans and a movable flange movable axially of said fixed flange and saiddrive output means; disc spring means urging said movable flange of saidsecond pulley axially toward said fixed flange thereof; and meansdrivingly interconnecting said first and second pulley means, the speedrelationship therebetween being determined by said centrifugallyresponsive means; said disc spring being coupled by friction at itsouter periphery only to said drive input means and said disc springmeans being coupled by friction at its outer periphery only to saiddrive output means.